There is known a method for recording a moving image while compressing it such as H.264/Moving Picture Experts Group-4 Advanced Video Coding (MPEG-4 AVC) (hereinafter referred to as “H.264”) (International Organization for Standardization/International Electrotechnical Commission (ISO/IEC) 14496-10: 2004, “Information technology—Coding of audio-visual objects—Part 10: Advanced Video Coding”). The H.264 coding method is widely used in, for example, one-segment digital terrestrial broadcasting. The H.264 coding method is characterized in that this method performs an integer transform per unit of four-by-four pixels and prepares a plurality of types of intra predictions (intra-picture predictions), in addition to the conventional coding method. Other characteristics of the H.264 coding method are that this method uses a loop filter, allows reference to a plurality of previous and subsequent frames, and provides motion compensation with use of seven types of sub blocks. Further, as is the case with the MPEG-4 method, the H.264 coding method can perform motion compensation with quarter pixel precision. Further, the H.264 coding method is characterized by use of, for example, universal variable length coding and context-adaptive variable length coding as entropy coding (“H.264: Advanced video coding for generic audiovisual services” published by International Telecommunication Union Telecommunication Standardization Sector (ITU-T))
The H.264 method has a plurality of modes for an intra prediction, and therefore bits should be assigned and coded for intra prediction mode information for identification of a selected mode as side information. For example, an intra prediction predicts a block from the surrounding blocks for each block constituted by four-by-four pixels in a macro block, and further estimates the prediction mode of the pixel block from the prediction modes of the surrounding blocks. Then, one bit is assigned to a flag (prev_intra4×4_pred_mode_flag) indicating a match/mismatch between the predicted mode and the estimated mode. Subsequently, in a case where the predicted mode does not match the estimated mode, three bits are assigned to a flag (rem_intra4×4_pred_mode) indicating the predicted mode for each block.